Rooibos doesn't seem to brew multiple times as well as real tea does. I think that goes for most herbal teas. Sometimes I do if I just want something else to keep sipping on but it's always going to be not as strong.

In my experience when you try and rebrew it, it definitely tastes more bland, but you can rebrew it. What I use as a rule of thumb is that I use half the amount of water as I did the first time, and brew it for twice the amount of time and it comes out alright. I wouldn't recommend trying a third steep

Generally I do the first brew for 4:30 to 5:00 minutes. I've tried it a few times at varying temperatures and times, but I haven't been able to find a second brew I really like. A lot more of that mouth-dryness is evident, and less of the earthy notes.

One thing that has not been mentioned yet is that flavored teas are often meant to give all the added flavor elements on the first infusion, so may not have much left or may have oddly unbalanced flavors left on reinfusion.